start=1
The secret here is the power of sed.
increment=5
lines=`cat linesfile.txt|sed -n "$start","$increment"p`
Basically the example above would take the first 5 lines from the file. You could change it though to say take 20 lines starting from the 5th line by adjusting the start and increment values.
bash, linux, extract, filestart, increment, linesfile, txt, sed, quot, adjusting,